Assessment is considered a powerful tool for improving learning outcomes and education quality. However, limited empirical research on classroom assessment exists in many developing countries including Ghana. This study explores the issues of mathematics classroom assessment in Ghana. Specifically, it investigates and analyses mathematics teachers' views and practices of assessment with specific reference to the implication for learning. Although the main focus of this study is on teachers' assessment practices, an examination of their conceptions of the nature of mathematics is undertaken to facilitate an in-depth understanding of teachers' views and practices. The research is mainly qualitative by design and employs both interpretative and exploratory strategies. Classroom observations, semi-structured interviews and document reviews are used as instruments for data collection through a non-participant observation method. A purposive sampling method is used to select six participants: four teachers and two headteachers for the study. This research study explores key factors affecting assessment practices in mathematics classrooms. In particular, it provides an analysis firstly of teachers' views about assessment emphasising improvement and accountability and secondly of the different types of knowledge, beliefs and attitudes of the mathematics teachers, and their relationship with practice. Attention is directed to the teacher's practical knowledge of teaching, of mathematics and how assessment comes into play. Also notable is the importance attached to the teachers' beliefs concerning the nature of mathematics. Findings from this study show that teachers use both formal and informal assessments in mathematics classrooms although formal assessment dominates practice. Teachers' views about assessment and their conceptions of the nature of mathematics are related to their classroom practices. Beyond these two factors, this exploratory study illustrates how teachers' assessment practices are affected by a number of contextual factors which are related to institutional policies, professional development and classroom conditions. There are implications of this research for the implementation of assessment for learning in Ghana. It is evident that in the current context, the widespread implementation of assessment for learning is ambitious and would demand well-defined and context-specific approaches to classroom practices. The introduction of these innovative assessment practices marks a significant departure from traditional practice and as such may require regular professional support and a coordinated and collaborative effort from policy makers, schools and teachers.